1. Field of the Invention
The invention relates to a method for forming and testing a semiconductor wafer, by which the frequency of cleaning test probes is significantly reduced, and, more specifically, to a method for forming and testing a semiconductor wafer, by which the residual of metal oxide remaining on metal pads of the semiconductor wafer can be reduced, and the chance of the residual stuck onto the test probes can be diminished.
2. Brief Description of the Related Art
Titanium-tungsten alloy is one of barrier-type metals treated as an adhesion/barrier layer to prevent the occurrence of interdiffusion in semiconductor connector. Titanium-tungsten film, of 10% Ti and 90% W by weight, is layered onto a substrate under a sputtered gold film as a seed layer for following a plating process.
Electroplating provides the electrochemical reaction to deposit Au onto the seed layer with a covered layer of patterned photoresist. Then, the continuous seed layer and UBM layer have necessary to completely remove by the Au etching and TiW etching sequentially in order to prevent interbumps connection electrically.
However, it always results from a residual problem to the TiW surrounded Au Bumps with this set of etching process. The significant amount of residue that is discontinuously distributed throughout all of the bumps presents a shape in elliptic or sheet-like within an order of magnitude of 100 nm. The presence of residue over bumps will cause a contamination problem to the following chip probing test of bumped wafers.
The test probes may be needed to make the electrical contact with Au bumps in order to thoroughly analyze a chip circuit. Thus, the probe heads often undergo residue remaining on Au bumps and the test probes, if contaminated, need to be cleaned by cleaning sheets during chip probing (CP) test. As above description, analysis misses without cleaning tips of test probes could happen after a number of probe touchdowns. As a result, a chip probing retest need to be carried out, if required, due to the low reliability in the probing test.
A frequent cleaning cycle to the test probes is necessary, and thus time cost increases to a proprietor. Moreover, the great amount of residue on the rough surface of Au bumps has been found experimentally.